Yet another newbie with ABS

Recommended Posts

Finally needed to resort to the forum since I have been stuck for about 1 week now on trying to print ABS. Ok, so here is the problem:

I have been itching to print in ABS for a while. All of my PLA prints have come out great but ABS is a challenge. The heater bed I have created is a MK1 (the red one with a hole in the middle for a thermistor). I decided to use an Arduino and create my own heat bed control code and circuitry. This has been tested and works great (displays temp on LCD). It has been mounted and leveled on the printer. When all this was done, I purchased some ABS plastic from here: http://www.protoparadigm.com/3mm-abs/

It is the tangerine color one if that matters any. After recieving it, I tried out a first print. It extruded fine enough and it printed a few first layers of my model. But after layers, it did not stick well enough and began to lift off the bed (I think because the bed was not hot enough and the cooling fan messed it up). So I tried again....and again...and again... until it was barely extruding. So I figured I had a clog. No biggie, just took the nozzle, brass thread, and PEEK apart. I acetone bathed the brass parts and then torched them to 1300 degree F to vaporized the rest of the plastic. I took a look through a microscope and it seemed that both brass parts were clean.

I installed the parts again (well, after I re-tapped the PEEK, man that thing was initally threaded terribly) and tried to manually extrude. It seem to be fine but it was slow at a temp of 235 degree C. I don't know how ABS flows but it seemed it wasn't good enough. I pushed some plastic with a flat tipped screw and the ABS came out ok but it took a little force. I tried highering the temp but that turned the plastic brownish so I imiediately went back to 235, got the clean orange again. I tried printning and nothing what so ever comes out (well, hardly any, not enough to stick on the bed). I checked tthe stepper gear for the filament feed and I can manually move throughthe Bowden tube just fine. I tried pushing filament again and tried to print again, no go.

SO before I go an clean it again (I don't think its clogged though, more like a desperate attempt) is there some magic recipe I do not know about? I mean, I have read other threads and people have similar issues but don't seem to get around the issue. I'd like to get annother nozzle doesn't Ultimaker have other vendors in the world? Maybe near or at the US?

Share this post

Link to post

Share on other sites

Some people mess up their flow setting and set it to 1 (1%) instead of 115% or so needed for ABS. Could this be it?

Turn the extruder gear by hand when the nozzle is at temp. How does it feel? Does it come out all nice and squirty? Raise the temp just a bit - 5C at a time. Maybe the spring in your extruder setup slipped and needs tightening? Look at the delrin wheel inside the extruder carefully. Does it spin? Does it have a flattened side to it? Is it jammed?

My flow control is at 120%. Though, when the first try with ABS was done, it seemed to print okay. As of now, it does not come out nice and squirty like the PLA does when I print with it. The extruder spring seems okay. I can feed filament in manually and I can actually see the plastic move up and down on the bowden tube. I will post some burned and non burned plastic when I get the chance to give you guys a better idea of what I am seeing.

Is there still a community brewing in NYC? I am thinking I should get a replacement nozzle and threaded brass piece, maybe this might fix my problem but shipping from the Netherlands is something I looking to avoid if I can help it. I don't like the shotgun approach to troubleshooting but I am getting stumped on what to do.

@All

I also stuck the heater bed arduino code in the public dropbox link. I figured someone may find it useful. It's not PID or state space or any other fancy control algorithm, just a simple on/off control. When the whole setup works completely, I can post the final code and schematic.

Share this post

Link to post

Share on other sites

I agree with Joergen. Plus 3% is the most you should need for a flow tweak. If you are running high flow tweaks to fix under-extrusion problems), the problem is probably due to filament feeder slippage (not necessarily resulting in visible grinding, as illuminarti has also observed and reported). The slippage occurs at filament feed volumes well under 10 mm ^3 /sec with the standard 0.40 mm nozzle. To some extent, you can crank the flow setting or flow tweak way up and compensate for the problem, but it's better to just slow down. I've done quite a bit of testing with 0.25, 0.35, 0.40, and 0.50 nozzles. The 0.35 is barely usable for ABS (obviously at slow extrusion rates) and I find the 0.40 mm nozzle to be marginal. The 0.25 nozzle is only useful wih PLA, if one accepts the additional challenges.

Joergen is using a 0.50 mm (or a bit larger) nozzle and my nozzle also measures 0.50 mm. Even with a 0.50 mm nozzle, sustained 10 mm ^ 3 / sec ABS extrusion can be quite iffy (10 mm ^3, /sec is often considered the upper limit for PLA with a 0.40 mm nozzle).

Mostly I recommend that you try a larger nozzle and higher nozzle temperatures. The feed pressure required goes down with increasing nozzle temperature. Also, I've done extensive destructive testing of my ABS parts using a torque wrench and my parts are always stronger with increasing nozzle temperature. The problem becomes the service limits of the hot end materials (PEEK and Teflon are both good for only 260C or so in long term service) and the increased likelihood of hot end jams at higher temperatures. Joergen and I have made simple mods to our hot ends that provide a bit more temperature headroom. (I'm very comfortable printing at 275 C, which is my standard nozzle temperature for Ultimachine black ABS). I never print any ABS below 240 C.

The next item on my wish list is a more powerful filament feeder. Either the one that mooncactus has developed or perhaps I might work on refining this dual counter-roatating drive feeder. I'm certain that a stronger feeder will enable higher print speeds or smaller nozzle orifices

I have the Ultiamaker V3 drive "hobbed bolt" (it's really a knurled stud) so I made a conventional hobbed bolt to try. It did offer more power than the V3, but it was very intolerant of any grinding. Once it started to grind, it was game over, and it had to be removed for cleaning with a dental pick. I re-installed the more fault tolerant and easy-to-clean V3.

I print ABS on heated bare glass, Kapton, and PET. Bare glass is very convenient but far more challenging than printing PLA on heated bare glass. Kapton and PET are equivalent. I recommend them to start, because the first layer settings become far less critical when using tape. You can experiment with "ABS juice" too, if you need better adhesion between the ABS and the tape. In fact, "aged" Kapton and ABS juice can be too strong! I'm up to a total of three broken hot-swappable glass plates!

It's best to leave the fan off for at least the first couple of layers and most ABS prints require little fan (but there are times when its essential). My process parameters are quite complicated at times and highly dependent on what I'm printing, but I've written enough for now, I think. Good luck and let us know of your progress.